Thiophene-2-carboxaldehyde thiosemicarbazone and certain substitution derivatives



United THIOPHENE-Z-CARBOXALDEHYDE THIOSEMI- CARBAZQNE AND CERTAIN SUBSTITUTION DERIVATIVES Le Roy W. Clemenee, Highland Park, and Herman J.

Eichel, Waukegan, 11L, assignors to Abbott Laboratories, North Chicago, IlL, a corporation of Illinois No Drawing. Application May 11, 1950, Serial No. 161,487

11 Claims. (Cl. 260-329) and compounds having substitution in positions 3, 4 and 5 of the thiophene ring as numbered above.

We have found that the more preferred compounds of our invention, so far as prolonged duration of therapeutic effect is concerned, to be the thiophene-Z-carboxaldehyde thiosemicarbazones of the formula:

wherein R and R are members selected from the class consisting of hydrogen, halogen, nitro, amino, alkyl and alkacylamido groups, wherein the alkyl and alkacylamido groups contain from 1 to 4 carbon atoms inclusive.

The most preferred compounds of our invention are those in which either or both of R and R is a halogen atom. By halogen, we refer to the chlorine, bromine and iodine atoms. We have discovered that the chlorine substituted thiophene ring compounds are the most effective. This is particularly true when the halogen or more particularly the chlorine atom is substituted in the 5-position.

The compounds of our invention may be very easily prepared by condensing the desired thiophene-Z-carboxaldehyde with thiosemicarbazide. This reaction may be illustrated by the following equation:

The reaction is carried out preferably in the presence of an organic solvent, and We have discovered ethanol to be the preferred solvent. The products of the invention are quite insoluble in water and they may be precipitated more completely from the ethanol by the addition of water.

tates Patent 0 In most cases the compounds of the invention are only slightly soluble in ethanol, and they may be purified by recrystallization from ethanol.

In order more clearly to disclose the nature of the present invention, several specific examples illustrating the preparation of typical compounds will hereinafter be described. It should be understood, however, that this is done solely by way of example and is intended neither to delineate the scope of the invention nor limit the ambit of the appended claims.

EXAMPLE I S-chloro-thiophene-Z-carboxaldehyde thiosemicarbazone About 18 gms. (0.123 mol) of 5-chloro-thiophene-2- carboxaldehyde and 11.2 gms. (0.123 mol) thiosemicarbazide are refluxed in cc. of absolute ethanol for about 7 hours and then permitted to stand for apuroximately 12 hours in the refrigerator. At the end of this period, crystalline material precipitates from the alcohol and is filtered oif, and more material crystallizes upon the addition of water to the filtrate. These two crystalline portions are treated twice in alcohol solution containing decolorizing charcoal, in which the solution is completed by warming. The solution is filtered while Warm, and the filtrate permitted to cool at which time the crystalline product precipitates from the solution. The precipitate is then recrystallized twice from ethyl alcohol and dried in a vacuum dryer at 50 C. The material produced has a melting point of 1578 C. The theoretical nitrogen, car bon and hydrogen contents of the above compound are 19.12%, 32.80% and 2.75% respectively. Upon analysis the material produced was found to have the following percentages; 19.22% nitrogen, 32.96% carbon and 2.70% hydrogen.

EXAMPLE II 5-brom0-thi0phene-Z-carboxaldehyde thiosemicarbazone Approximately 6.2 grns. (0.032 mol) of S-bromo-thiophene-Z-carboxaldehyde is dissolved in 25 cc. of absolute ethanol and 2.9 grns. (0.032 mol) of thiosemicrabazide is introduced to the solution. By proceeding as in Example I, the above crystalline compound having a melting point of 1745 C. is obtained. The theoretical nitrogen content for the above compound is 15.91%. Upon analysis the material obtained was found to have a nitrogen content of 15.86%.

There may also be produced in accordance with the invention 5 iodo thiophene-2-carboxaldehyde thiosemicarbazone when 5-iodothiophene-2-carboxaldehyde is used in accordance with the process of Examples I or II.

EXAMPLE III Thiophene-Z-cqrboxaldehyde thiosemicarbazone About 3.2 gms. of thiophene-Z-carboxaldehyde and 2.44 gms. of thiosemicarbazide are refluxed in 50 cc. of absolute ethanol and the reaction mixture treated as in Example I. The re-crystallized material is found to have a melting point of 1824 C. and a nitrogen content of 22.50%. The theoretical nitrogen content for the above compound is 22.70%. I

3 EXAMPLE 1v S-mezhyl-thiophene-Z-carboxala'ehyde thiosemicarbazone s H cmUcnqwrr-oasm About 3.16 g. of S-methyl-thiophene-Z-carboxaldehyde and 2.29 g. of thiosemicarbazide are refluxed in ethyl alcohol and treated in accordance with the procedure of Example I. Upon recrystallization the material is found to have a melting point of 142-4 C. and a nitrogen content of 20.51%. The theoretical nitrogen content for the above compound is 21.1%.

EXAMPLE V 3methyl-5-nitr0-thiophene-Z-carboxaldehyde-Ihiosemicarbazone About 2.87 g. of 3-methyl-S-nitro-thiophene-2-carboxaldehyde diacetate and 0.92 g. of thiosemicarbazide are refluxed in a mixture containing 40 cc. of water, 10 cc. of ethanol and 3 cc. of concentrated sulfuric acid for 8 hours. The dark brown precipitate formed is de-colorized and recrystallized in accordance with the procedure of Example I and found to have a melting point of 212-215 C. with decomposition. The nitrogen content is found to be 21.89% as compared to the theoretical percentage of 22.00% for the above compound.

, EXAMPLE VI 5 -nitr-thiophene-Z-carboxaldehyde thr'osemicarbazone About 1.5 g. of S-nitro-thiophene-Z-carboxaldehyde diacetate and 0.6 g. of thiosemicarbazide are refluxed in a mixture containing 40 cc. of water, 10 cc. of ethanol and 3 cc. of concentrated sulfuric acid for 8 hours. The precipitate is then purified in accordance with the procedure of Example I yielding a red material having a melting point of about 24550 C. with decomposition. The material was found to have a nitrogen content of 24.29% as against a calculated percentage of 24.33

EXAMPLE VII -amino-thiophene-Z-carboxaldehyde thiosemicarbazone There may be also produced in accordance with the invention compounds having a lower alkyl substituent in which the alkyl substituent contains up to 4 carbon atoms on any one of the three available positions of the thiophene ring. For example, there may be produced S-methyl-thiophene-2-carboxaldehyde thiosemicarbazone, 4-ethyl-thiophene-Z-carboxaldehyde thioscmicarbazone and S-n-butylthiophene-Z-carboxaldehyde thiosernicarbazone when the intermediates are 3-methyl-thiophene-2-carboxaldehyde, 4-ethyl-thiophene-Z-carboxaldehyde, and S-n-butyl-thiophene-Z-carbo-xaldehyde, respectively.

Of the lower acylamido compounds which may be produced in accordance with the invention, there are several compounds having a lower alkacylamido group of which the alkacyl moiety contains up to and including four carbon atoms, of which are the following compounds: 3-acetylamido-thiophene-2-carboxa1dehyde thiosernicarbazone, S-n-butyrylamido-thiophene-2-carboxaldehyde thiosemicarbazone.

Of the thiophene-2-carboxaldehydes used in accordance with the process of preparing the above compounds, most are novel compounds. Most of these compounds are disclosed in the copending application of Arthur W. Weston, Serial No. 92,961, filed May 12, 1949, now U. S. Patent No. 2,601,479. In general, it may be said that where the substituents on the thiophene ring are other than nitro, amino and acylamido, the desired thiophene-Z-carboxaldehyde may be produced by treating the corresponding thiophene compound with N-methyl-formanilide and phosphorous oxychloride. Where it is desired to prepare a nitro substituted compound, it is desirableto prepare the corresponding aldehyde diacetate following which this compound is nitrated. For example, the compound 5- nitro-thiophene-Z-carboxaldehyde diacetate used in the preparation of Example VI may be prepared as follows.

EXAMPLE VIII S-nitro-thiophene-Z-carboxaldehyde diacetate About 13 g. of fuming nitric acid is added slowly with stirring to 120 cc. of glacial acetic acid at 5 C. While maintaining the temperature at about 5 C., 22.4 g. (0.2 mol) of thiophene-Z-carboxaldehyde dissolved in cc. of acetic anhydride is added dropwise with stirring. The mixture is then stirred for 5 hours and allowed to stand for about one-half day. The solution is then poured in an equal volume of ice water and a yellow precipitate forms. The crystalline precipitate is recrystallized from ethyl alcohol using water as the precipitating agent. After drying in a vacuum desiccator, the above compound is formed having a melting point of 66-8 C.

The intermediate 3-methyl-5-nitro-thiophene-2-carboxaldehyde diacetate used in Example V may be prepared by treating 3-methyl-thiophene-2-carboxaldehyde in accordance with the procedure of Example VIII. This compound is a yellowish crystalline material having a melting point of 43-4 C.

The amino substituted thiophene-Z-carboxaldehydes may be produced by reducing catalytically, the corresponding nitro-thiophene-2-carboxaldehyde.

Acylamido compounds may be prepared by treating the corresponding amino-thiophene-2-carboxaldehyde with the corresponding carboxylic acid anhydride or acid halide.

The compounds of the invention may be administered to patients in various ways. We have discovered that they may be administered orally, and thus it is possible to supply the medical profession with a therapeutic agent for the treatment of tuberculosis without necessitating parenteral administration. Accordingly, the physician may prescribe tablets, capsules and solutions which may be administered-by the patient without demanding the services of a physician or nurse for each administration. Dosages in the form of capsules and tablets are, of course, the most convenient from the standpoint of the pharmaceutical industry, and the following is an example of a 100 mg. tablet of a representative compound, accord ing to the invention.

EXAMPLE 1X Formula for 100 tablets:

The tablets are prepared by mixing the S-chloro-thiophene-2-carboxaldehyde-thiosemicarbazone with lactose, screening, and moistening slightly. This mixture is granulated with a corn starch paste made by dissolving 2 gms. of corn starch in cc. of water with heat. After completion of the granulation, the preparation is dried thoroughly at 100 F. To this granulation is added the talc, magnesium stearate and the 6 gms. of dried corn starch. After thoroughly mixing, the tablets are compressed in a conventional tablet machine.

Inasmuch as the compounds according to the invention are not too soluble in water, it is advantageous to dispense them in the form of a tincture having a fairly high concentration of ethyl alcohol or in a solution contained in an organic solvent such as propylene glycol.

Others may readily adapt the invention for use under various conditions of service, by emloying one or more or the novel features disclosed, or equivalents thereof. As at present advised with respect to the apparent scope of our invention, we desire to claim the following subject matter.

We claim:

1. A compound of the formula:

wherein R is selected from the class consisting of hydrogen, chloro, bromo, nitro, amino and alkyl group having between 1 and 4 carbon atoms inclusive, and R is selected from the class consisting of hydrogen, chloro and bromo.

2. The compound 5-chloro-thiophene-2-carboxa1dehyde thiosemicarbazone.

3. The compound 5 bromo thiophene 2 carboxaldehyde thiosemicarbazone.

4. The compound 5-methyl-thiophene-Z-carboxaldehyde thiosemicarbazone.

5. The compound 5-nitro-thiophene-2-carboxaldehyde thiosemicarbazone.

6. The process of preparing S-chloro-thiophene-Z-carboxaldehyde-thiosemicarbazone, which comprises refluxing 5-chloro-thiophene-2-carboxaldehyde with thiosemicarbazide.

7. The process of preparing S-bromo-thiophene-Z-carboxaldehyde thiosemicarbazone, which comprises refluxing S-brorno-thiophene-Z-carboxaldehyde with thiosemicarbazide.

8. The process of preparing thiophene-Z-carboxaldehyde thiosemicarbazone, which comprises refluxing thiophene-Z-carboxaldehyde with thiosemicarbazide.

9. The process of preparing S-methyl-thiophene-Z-carboxaldehyde thiosemicarbazone, which comprises refluxing 5-methyl-thiophene-2-carboxaldehyde with thiosemicarbazide.

10. The compound, 2 thienylaldehyde thiosemicarbazone having the structural formula:

11. The process of producing a compound according to claim 1 which comprises refluxing a thiophene-Z-carboxaldehyde of the formula RI .L

0110 s wherein R is selected from the class consisting of hydrogen, chloro, bromo, nitro, amino and alkyl group having between 1 and 4 carbon atoms inclusive, and R' is selected from the class consisting of hydrogen, chloro and bromo, with thiosemicarbazide.

References Cited in the file of this patent UNITED STATES PATENTS White June 15, 1943 Stillman Feb. 18, 1947 OTHER REFERENCES vol. 59, pp. 675- 

1. A COMPOUND OF THE FORMULA: 